It is well known that a Fourier Transform Matrix (FTM) can be used in a multi-carrier RF communication system for distributing a plurality of RF signals among multiple amplified paths, and for recovering the plurality of RF signals after amplification. Advantages associated with using the FTM include a reduced peak-to-average power requirement for the amplifiers, greater efficiency of amplifier utilization, and a degree of redundancy.
Unfortunately, the redundancy provided by the prior-art FTM technique is not perfect. When a failure occurs in one of the amplified paths, the insertion loss encountered by each of the RF signals is degraded, and the isolation between the RF signals is also degraded. For example, in a 4×4 FTM, if a singular amplified path is disrupted, insertion loss for each RF signal will degrade by approximately 2.5 dB, and the isolation between the RF signals will be reduced substantially—in some cases by 30 to 40 dB.
Thus, what is needed is a method and apparatus for facilitating fault tolerance in an RF amplifier system. The method and apparatus preferably will tolerate a failure in one of the amplified paths with minimal degradation of insertion loss and without producing a substantial reduction in isolation between the RF signals.